Lamp fitting



Nov. 1, 1966 J. MULLER ETAL 3,283,145

LAMP FITTING Filed Aug. 13, 1963 2 Sheets-Sheet 1 JHiIIer .E. 1.81229 A TTYS Nov. 1, 1966 J. MULLER ETAL LAMP FITTING 2 Sheets-Sheet 2 Filed Aug. 13, 1963 FIG. 4

fii M United States Patent 3 Claims. Cl. 240-128 This invention relates to improvements in and relating to lamp fittings.

It is known in the art to attach the transparent bowls to the lamp housingsby means of clamping arms. These clamping arms form part of rotatable clamping members arranged inside the lamp housing and can be operated from the outside of the lamp. The rotatable clamping arm is first horizontally rotated to permit the bowl to be placed in position into contact with a co-operating sealing strip, and when this is done the rotatable member is rotated back by means of an operating lever on the outside of the lamp housing until its arm slides under an inside shoulder formed in the bowl and presses the rim of the bowl tightly against said sealing strip. The rotatable clamping members are usually made of sheet metal of suitable gauge strong enough to retain the bowl in position.

However, the clamping members commonly used are in practice open to several objections. For instance, they occasionally tend to jam so that considerable effort is needed to turn them into clamping position. This often causes the clamping members to bend and distort. Also, the pressure applied to the transparent bowl may be considerable and, if the said bowls are made of synthetic plastics material, cold flow of the synthetic plastics material may lead to permanent deformation. Moreover, the horizontal portion of the rim of the bowl often tightly presses against the vertical skirt of the housing and this prevents the bowl from freely expanding.

Just as frequently the rotary clamping and retaining member is found to work far too easily, in which case it fails to press the rim of the bowl sufiiciently tightly on to the sealing strip. In order to overcome these drawfbacks it has been the practice to keep rotary retaining clamps of different sizes in stock. Clearly this is an added nuisance because when assembling the fitting only trial and error can show which is the right size of clamp for the particular tolerations exhibited by the parts of the fitting. Moreover, retaining clamps which vary in thickness within the range of say 0.5 and 1.5 mm. are not easily distinguished during assembly, and faulty assembly aggravates the trouble rather than providing a remedy.

The present invention seeks to eleminate the causes which lie at the root of the trouble. These causes must be sought in the combined additive effect of dimensional tolerations of the several components constituting the fitting. In other words, allowance must be made for tolerational variations of the rim and thickness of the bowl, the skirt of the housing and the size of the sealing strip. For example, if the gauge of the transparent plastics material of the bowl happens to exceed the design gauge by a positive toleration (and this can easily occur in extrusion) and the height of the rim also has a positive toleration (and this may also easily be the case), then the sum of both tolerations may causeexcessive pressure by the clamping member because the distance between the levels of the clamping face of the clamping member and the level of the sealing strip on the housing will exceed the distance for which the clamp was designed. This effect may be further accentuated if variations in the gauge of the sheet metal of the lamp housing are responsible for variations in the length of the skirt and if the thickness of the sealing strip is likewise subject to slight variations. Also if the distance of downward offset of the clamping member is slightly less than that of the actual design measurement further undesirable increases in the clamping pressure may be the result.

Conversely, existing tolerations may .be additive in the opposite direction, and the clamping pressure may be insufiicient, for instance if the degree of offset is excessive and the gauge of the material in the shoulder of the bowl is too small.

With due regard to these facts the present invention provides a lamp fitting which comprises a transparent bowl with an inwardly offset vertical rim for cooperation with a sealing strip on the underside of a lamp housing, an externally operable rotatable clamping member attached to said housing for engagement of the underside of a shoulder formed by the inward offset disposition of said vertical rim of the bowl, said clamping member having sufiicient elastic resilience and deflectability to allow for the maximum possible tolerational variations in the relative positions of all the cooperating parts, such as are due to tolerationa-l variations in the dimensions of said transparent bowl, said housing, said clamping member and said sealing strip, and the free end of said clamping member which engages the underside of said shoulder being provided with a sloping surface arranged like a ramp of appropriate height for the necessary yielding deflection of said clamping member upon being rotated into engagement with the underside of said shoulder.

The sloping surface is preferably constructed for a deflection of the free end of the rotatable clamping member within a range of about three millimeters in conformity with the elastic deflectability range of said clamping member.

It is clearly important that the clamping member should always be capable of applying adequate pressure for firmly retaining the bowl in tight contact with the sealing strip. This must apply even when all the existing tolerations are additive in the direction of reducing said pressure, that is to say if the rim of the bowl is too low and the degree of offset of the rotary clamping member excessive. The conformation and elasticity of the clamping member must be sufiicient in such extreme cases still to apply the required spring pressure.

Conversely, the clamping member must be capable of satisfactory operation when all the existing tolerations combine to increase the clamping pressure, for instance if the thickness of the bowl wall is excessive and the rim of the bowl is too high, and .the actual elevational offset of the rotary clamping member too small. 'In such circumstances the contacting surface of the clamping member may fail to slide under the shoulder at all. The bottom edge of the ramp-like surface which may generally be produced by imparting to the end of the clamping member an arcuate cam-bere-d shape must be below the lowest possible level of the underside of the shoulder of the bowl. This will ensure that the clamping member will slide underneath the shoulder, and the inherent elasticity of the clamping member must then be suflicient to yield until the bowl is securely held. The clamping pressure when the clam-ping member thus yields must not rise to an extent likely to cause the transparent bowl to be damaged. The increase in spring pressure should not exceed thirty times the Weight the clamping member is intended to support. On the other hand, it should not be less thanten times this weight. In both cases the resilience of the clamping member must still be within the elastic range to prevent the clamping member from being permanently deformed.

Several preferred embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is a fragmentary vertical cross section through a first embodiment of the invention;

FIG. 1a is a vertical section through the operative end of the clamping member;

FIG. 2 is a top plan view of FIG. 1;

FIGS. 3 and 4 are fragmentary vertical cross sections through further embodiments of the invention;

FIG. 4a is a vertical cross section through FIG. 4;

FIGS. 5 and 6 are fragmentary vertical cross sections through still further embodiments of theinvention; and

FIG. 7 is a fragmentary vertical cross section through a lamp fitting showing the resilient deflectability of the clamping member.

FIG. 1 shows a lamp housing 1 consisting of sheet metal and formed with a lateral skirt or downward flange 2. The reference numeral 3 denotes a conventional sealing strip.

Part of a transparent plastic bowl of the fitting is seen at 4. 5 is a horizontal inwardly directed shoulder of the bowl 4 and 6 is a vertical rim which bears against the sealing strip 3.. The vertical rim 6 is pressed against the sealing strip 3 by a rotary retaining and clamping member 7 which has a substantially horizontal arm 8 adapted to be rotated laterally into engagement with theunderside of the shoulder 5 of the transparent bowl 4.

The rotary clamping member 7 can be operated through the intermediary of an external lever 9 on the lamp housing 1. This lever 9 has asaucer-shaped circular depression 10 which projects into a circular opening 11 in the lamp housing.

The centre of the saucer-shaped circular depression 10 is formed with a downwardly and then inwardly extending flange 14 which serves the operating lever 9 to a retaining plate 12 and to a second horizontal arm 13 of the clamping member 7 Instead of providing a special retaining plate 12 the second horizontal arm 13 of the clamping member 7 may be suitably constructed to serve as a retaining plate, and one component can thus be saved.

In the illustrated embodiments the clamping member 7 is entirely made of spring steel. The elastic flexibility of the steel must be sufficient to provide an adequate though not excessive amount of spring pressure, irrespectively as to whether the relevant tolerations are all additive in the direction of reducing or increasing the pressure. Moreover, the general conformation of the clamping member 7 including the amount by which the deflectable arm 8 is offset must be suchas to ensure that even when all the t-olerations addin the direction of reducing the pressure the clamping arm 8 will still bear against the underside of the shoulder 5 of the bowl 4 with an adequate amount of pressure. In cross section the horizontal arm 8 of the clamping member 7 is formed with a camber to providea sloping entry surface in the form of a ramp, as shown in FIG. 1a. The height of the ramp is suflficient to permit the arm 8 to slide under the shoulder 5 even when all the tolerations are additive in the direction of increasing the clamping pressure.

. In the embodiment illustrated in FIG. 3 a clamping member is held in position by a bolt 21 placed with its head 22 hearing against the outer side of the housing. The bolt 21 has a square sectioned portion 23 which fits into a corresponding hole in, the clamping member. A spring 24 which embraces the shaft of the bolt 21' and which is held by a nut 25 provides the resilient clamping pressure between the clamping member 20 and the bowl. As will be understood the clamping member 20 is axially movable on the bolt 21. As set forth above, the distance the clamping member 20 can yield on the bolt 21 must be sufficient to provide adequate but not excessive clamping pressure for any combination of tolerational variations. In this form of construction the clamping member 20 itself need not be inherently elastic.

-In the embodiment illustrated in FIG. 4 a clamping member is provided with a flexible joint 31 which per- 4 l mits the member 30 to swing about, a horizontal hinge pin 32 (FIG. 40). T he reference numeral 33 denotes a torsion spring for loading the clamping member 20.

In FIG. 5 the edge portion of a lamp housing 34 is formed with an upward trough and an operating lever 35 is suitably bent to extend over the top of the trough. This arrangement perm-its a clamping member 36 to be constructed with a less pronounced downward offset.

FIG. 6 shows a form of construction comprising a clamping member 38 made of synthetic plastics material, such as polyamide. In this embodiment the :clamping member 38 instead of the associated actuating lever 37 has a central saucer-shaped portion 39 which fits into a corresponding opning in the lamp housing. The inherent elasticity of the synthetic plastics material is suflicient to,

provide the required resiliency.

FIG. 7 schematically shows the upper .part of the housing and the required elastic deflectability of the clamping member. clamping member in the position it will occupy before a bowl or the like has been fitted. The full line is the position of the clamping member when holding and retaining a transparent bowl.

We claim:

1. A lamp fitting comprising a bowl having an inwardly directed annular shoulder and an outwardly directed annular rim adjacent said shoulder, a housing over. said bowl including an end panel in engagement with said annular rim, at least one clamping means internally of said housing, said clamping means having a first end portion adjacent said end panel and an opposite end portion having a cam ramp progressively movable to a posit-ion in clamping engagement with said shoulder, a clamping means ope-rating handle externally of said housing having a pivot means secured thereto which extends inwardly of said housing into engagement with said first end portion of said clamping means for rotation of saidclamping means into and out of engagement with said shoulder about .an axis formed by said pivot means, said first end portion of said clamping means being axially movable along said pivot means and having resilient means biasing said first end portion in the direction of said end panel, said clamping means thereby holding the bowl firmly but allowing for substantial positive and negative manufacturing tolerances in the bowl thickness at said shoulder, and in the height of said rim.

2. A lamp fitting comprising a bowl having an inwardly directed annular shoulder terminating in an upwardly directed annular rim, a housing having an end panel terminating in a depending peripheral skirt, said rim being received in said housing, a sealing gasket between saidend panel and said rim, a plurality of openingsin said end panel, a plurality of clamping members internally of said housing each having a first end portion adjacent an associated one of said openings and an opposite end portion movable to a position for underlyingly clampingly engaging said shoulder, a medial portion of each of said clamp mg members maintaining said first and opposite end por-.

tions in axially offset generally horizontal planes, a plu- I rality of handles each positioned externally of said housing having a first end portion adjacent an associated one of said openings and an opposite end portion remote firom said openings, means joining said first end portions through each of said openings for selectively rotating said clamping members by said handles, said joining means including a stud associated with each handle and clamping member, each clamping member being mounted for axial move ment relative to its stud, means for biasing each clamping member toward said end panel, and each opposite end portion of said clamping members having a cam ramp for progressively urging said rim against said sealing gasket as said clamping members are rotated toward a position,

with the cam ramps full-y underlying said shoulder 3. A lamp fitting comprising a bowl having an inwardly directed annular shoulder terminating in an upwardly The dotted lineindicates the outline of the directed annular rim, a housing having an end panel terminating in a depending peripheral skirt, said nim being received in said housing, a sealing gasket between said end panel and said rim, a plurality of openings in said end panel, a plurality of clamping members internally of said housing each having a first end portion adjacent an associated one of said openings and an opposite end portion movable to a position for underlyingly clampingly engaging said shoulder, hinge means joining said first and opposite end portions for swinging movement of said opposite end portions toward and away tfirom said end panel, means biasing said opposite end portions toward said end panel, a plurality of handles eadh positioned externally of said housing having a first end portion adjacent an associated one of said openings and an opposite end portion remote from said openings, means joining said first end portions through said openings for selectively rotating said clam-ping members by said handles, and each opposite end portion of said clamping members having a cam ramp for progressively urging said against said sealing gasket as said clamping members are rotated toward a position with the cam ramps full-y underlying said shoulder.

References Cited by the Examiner UNITED STATES PATENTS NORTON ANSHER, Primary Examiner.

20 C. CHALMERS LOGAN II, Assistant Examiner. 

1. A LAMP FITTING COMPRISING A BOWL HAVING AN INWARDLY DIRECTED ANNULAR SHOULDER AND AN OUTWARDLY DIRECTED ANNULAR RIM ADJACENT SAID SHOULDER, A HOUSING OVER SAID BOWL INCLUDING AN END PANEL IN ENGAGEMENT WITH SAID ANNULAR RIM, AT LEAST ONE CLAMPING MEANS INTERNALLY OF SAID HOUSING, SAID CLAMPING MEANS HAVING A FIRST END PORTION ADJACENT SAID END PANEL AND AN OPPOSITE END PORTION HAVING A CAM RAMP PROGRESSIVELY MOVABLE TO A POSITION IN CLAMPING ENGAGEMENT WITH SAID SHOULDER, A CLAMPING MEANS OPERATING HANDLE EXTERNALLY OF SAID HOUSING HAVING A PIVOT MEANS SECURED THERETO WHICH EXTENDS INWARDLY OF SAID HOUSING INTO ENGAGEMENT WITH SAID FIRST END PORTION OF SAID CLAMPING MEANS FOR ROTATION OF SAID CLAMPING MEANS INTO ANDOUT OF ENGAGEMENT WITH SAID SHOULDER ABOUT AN AXIS FORMED BY SAID PIVOT MEANS, SAID FIRST MEANS PORTION OF SAID CLAMPING MEANS BEING AXIALLY MOVABLE ALONG SAID PIVOT MEANS AND HAVING RESILIENT MEANS BIASING SAID FIRST END PORTION IN THE DIRECTION OF SAID END PANEL, SAID CLAMPING MEANS THEREBY HOLDING THE BOWL FIRMLY BUT ALLOWING FOR SUBSTANTIAL POSITIVE AND NEGATIVE MANUFACTURING TOLERANCES IN THE BOWL THICKNESS AT SAID SHOULDER AND IN THE HEIGHT OF SAID RIM. 